Mr Obama has incumbency in his favour, and foreign policy has been his strength.

He can point to successes like the raid that killed Osama bin Laden, and to keeping a campaign promise to end the war in Iraq.

But the contest is not perhaps as uneven as it used to be.

The Romney campaign has landed some blows by harnessing the turmoil in the Middle East, especially the death of the US ambassador to Libya, to argue that the Obama administration's foreign policy is unravelling.

Mr Romney has been making the case that the president has been weak on everything, including Iran's nuclear program and China.

Neck and neck

The Republican's dominance of the first debate revived his campaign after a series of stumbles, and although Mr Obama was strong in the second contest, polls have the pair neck and neck.

North America correspondent Jane Cowan canvassed the views of some fellow journalists who have been covering the campaign:

BBC correspondent Matt Frei

"The first one was much more exciting than people had thought, partly because there was such an extraordinary discrepancy between the way that the president was almost asleep at the switch and Romney turned out to be not to robotic after all, the man had a pulse and a brain and he spoke in perfect joined up sentences.

"The second one was of course like a sort of feisty boxing match.

"Well this one, who knows, I mean it's about foreign policy, which ostensibly America doesn't care that much about.

"On the other hand, the slightest thing could influence this election."

American ABC White House correspondent Jake Tapper

"It's tough but polls show that Mitt Romney has been drawing to parity when it comes to these issues; trusted to handle terrorism, trusted to handle international affairs.

"President Obama used to have a big advantage on those issues - he doesn't anymore.

"Whether it's because of Benghazi or more Americans paying attention, or a more forceful presentation from Mitt Romney, whatever it is, he actually is drawing closer to equality on those issues."

This has been an election in which debates have had an outsized effect on the race, even right back to the primaries, where Texas governor Rick Perry said 'Oops' when he lost his train of thought during one of those debates.

Mr Romney's surprising dominance in the first debate revived his campaign after a series of stumbles, and kickstarted the momentum that has made this a real contest.

It is unlikely though that the debate will necessarily change the dynamic at this juncture, but it will certainly be the final taste in many voters' mouths just two weeks before Americans cast their vote.